How to translate multiple words simultaneously in Ruby?

Question

I'm attempting to create a substitution translator for a language my friend and I created. In this language, certain things have to happen simultaneously and I can't figure out how to do that in Ruby.

With simple things like swapping the vowels around, i.e.

a --> u
i --> o
o --> i
u --> a

I've just done this:

input.tr("aiou", "uoia")

But I can't figure out a way to make the following translations occur simultaneously:

no --> e
e --> y
y --> el

so that the phrase "yellow rhino" would become "elyllow rhie".

Any suggestions or examples for what I can do? gsub? tr? Another method altogether?

Answer 1

First you define a substitution map:

MAP = {
  'a' => 'u',
  'i' => 'o',
  'o' => 'i',
  'u' => 'a',
  'y' => 'el',
  'no' => 'e',
  'e' => 'y'
}

Then you can make this into a regular expression to match all the "keys" in one shot:

SUBST = Regexp.union(MAP.keys)

This is handy because gsub can use these mapping tables to do substitution:

def translate(words)
  words.gsub(SUBST, MAP)
end

Which means you can do this:

puts translate("translate multiple words simultaneously")
# => trunsluty maltoply wirds somaltunyiaslel

tr is a great tool, but it's limited to single character substitutions. gsub can do everything tr can and more.